Implemented by the Organization of American States
Unit of Sustainable Development and Environment
for the USAID Office of Foreign Disaster Assistance and the Caribbean Regional Program
Kingston Multi-hazard Assessment
DRAFT Guidelines for Use of
Landslide Susceptibility Maps
Note: These guidelines are presented in draft
form, pending review, update and approval by appropriate Government of Jamaica Agencies
and other interested parties in Jamaica. These draft guidelines were developed by Rafi
Ahmad as part of the KMA landslide hazard assessment.
- Two landslide susceptibility maps have been prepared for the
Kingston Metropolitan Area: (i) Shallow Landslides Susceptibility Map, and (ii) Deep
Landslides Susceptibility Map. NOTE: For a detailed description of factor analysis and
susceptibility zones reference should be made to Publication no.5, Unit for Disaster
Studies, UWI, Mona, Kingston 7, Jamaica (also available at http://www.oas.org/en/cdmp/document/kma/udspub5.htm).
Submarine Landslide Susceptibility on the Palisadoes and other areas on the south coast
are beyond the scope of the present work.
- The susceptibility zones shown on the maps reflect variable potential for initiating a
landslide on a slope, but do not necessarily indicate how far the landslide will travel,
or where the landslide debris (or debris flow) will be deposited. Additional hazards from
landslide deposition may exist downslope from the high susceptibility regions shown, or at
the mouths of drainage basins with highly susceptible slopes.
- Land use planners, developers and general public may use these maps to determine areas
where landslides may be a problem in site development, and/or where reports from
geologists and geotechnical engineers should be required prior to undertaking any site
development activities. These maps can not be used to determine the hazard to any
individual structures or site development. These maps should not be used as a substitute
for detailed geologic/geotechnical site investigations. Slopes that are stable at the
present time may be rendered unstable by natural or man-made processes. These maps show
relative landslide hazard, that is, which areas are more hazardous than others. Areas of
high susceptibility to landsliding generally coincide with areas where there is high
incidence of landslides.
- Many of the areas of potential slope instability may be suitable
for development, even if landslides are present provided that correction/mitigation
strategies are employed based on comprehensive geologic and geotechnical evaluations and
advise. The geologic-geotechnical report should include an evaluation of existing ground
stability, proposed changes/alteration to drainage and topography, and recommendations for
remedial and/or preventive measures to improve and/or maintain slope stability. Permission
to develop the site must be approved by competent persons. The site report/s should be
available to the potential homebuyers.
- The accompanying Landslide Susceptibility Maps for Shallow and Deep Landslides include
five mapped susceptibility classes, based on landslide densities in each class. These
classes are based on: (I) For Shallow Landslides on landslide densities for active
landslides and slide zones only in 83 unique combinations of factors related to slope,
Aspect, Lithology, and Slope Curvature, and (II) For Deep Landslides on landslide
densities for Scarps-definite and Scarps-probable landslides only in 249 unique
combinations of factors related to Slope, Aspect, Lithology, and Distance to Faults.
- For general purpose use the range of landslide susceptibility are condensed into 4
categories: (a) Low susceptibility, (b) Moderate susceptibility, (c) Moderate-high
susceptibility and (d) High susceptibility which incorporates the original zones of very
high and high susceptibility containing identified active landslides.
Landslide Susceptibility Categories
Low Susceptibility (colour code blue): Areas for which the combination of
factors is generally unlikely to adversely influence slope stability. Site development to
be guided by normal planning and other building regulations.
Moderate Susceptibility (colour code green): Areas for which the combination
of factors is less likely to adversely affect the stability provided that the existing
ground conditions are not radically altered to facilitate site development.. The scale and
nature of proposed development should be taken into consideration.
Moderate-high Susceptibility (colour code yellow): Areas for which the
combination of factors may adversely influence slope stability. Slopes are covered with a
thick blanket of weathered rock and colluvium (debris) which when disturbed are prone to
landslides. Debris flows should be anticipated. Development may proceed based on
geologic-geotechnical investigations and advice (See Point 4
above). The cost of investigations and remedial and/or preventive measures are likely to
High Susceptibility (colour codes purple and red): Areas for which existing
ground conditions are likely to create serious landslide problems. It includes areas near
faults and fault scarps. In general, these areas are unsuitable for site development. The
cost of carrying out standard geologic-geotechnical investigations and remedial/preventive
work for slope stabilization may be very high. Therefore, it is best to avoid these slopes
as far as possible except for the most essential use. A thorough ground investigation
report by competent persons should be required before any site development is undertaken.